A progressive power lens has a part in which a power is progressively changed, and fields of view for viewing different distances (for example, a distance portion for distance vision, a near portion for near vision or the like) can be obtained by a single lens, and therefore the progressive power lens is mainly used as a glasses lens for correction for presbyopia.
Various progressive power lenses having various surface configurations are known, and one of them is a progressive power lens having a so-called both-sides composite progressive structure (for example, see Patent Literature 1). In the progressive power lens having the both-sides composite progressive structure, a power, which is progressively changed, is divided into a power change in a vertical direction of the lens (namely, an up and down direction in use of the lens) and a power change in a horizontal direction of the lens (namely, a left and right direction in use of the lens), and sharing rates in respective directions suitable for two surfaces of a front and a rear surfaces are defined, and thereby one progressive power lens is formed. Specifically, for example, a surface configuration in which the power change in the vertical direction of the lens having a progressive refractive power function is given to only an object side surface (namely, a convex surface), and the power change in the horizontal direction of the lens is given to only an eyeball side surface (namely, a concave surface) is adopted. In such a surface configuration, the front and the rear surfaces of the lens are formed in aspherical surfaces without having a progressive surface, respectively.
Accordingly, the progressive power lens having the both-sides composite progressive structure is structurally different from any of “an outer surface progressive power lens” in which a progressive surface is arranged on an object side surface, “an inner surface progressive power lens” in which the progressive surface is arranged on an eyeball side surface, and “a both-sides progressive power lens” in which the progressive surfaces are used for the front and the rear surfaces and a desired addition power is shared by the front and the rear surfaces. According to the progressive power lens having the both-sides composite progressive structure having such a surface configuration, both of an advantage of “the outer surface progressive power lens” in which a swing angle of an eyeball when a line of sight is moved between respective fields of view corresponding to different distances can be less, and an advantage of “the inner surface progressive power lens” in which a jumping and warping of images can be reduced by suppressing magnification difference between respective fields of view corresponding to the different distances can be obtained.
Here, in a glasses lens including a progressive power lens having a both-sides composite progressive structure, it is known as general technical common knowledge that to form a meniscus shape such that an object side surface is formed by a convex surface and an eyeball side surface is formed by a concave surface (for example, see paragraph [0031] in Patent Literature 1).